Digital Subscriber Line technology architectures, generally denoted as xDSL, allow digital distribution of data services with traditional narrowband voice transmissions.
One form of xDSL of particular interest to the present invention is VDSL (Very high bit rate Digital Subscriber Line), which is a packet-based transmission architecture used to provide high bandwidth distribution of digital video and data signals to customers. A VDSL-based architecture provides a single platform for supporting bandwidth-intensive applications, such as Internet access, remote LAN access, video conferencing, and video-on-demand, and is the only xDSL technology designed to handle the broadband requirements of video distribution.
VDSL services are typically implemented in an asymmetric form having a maximum downstream transmission capability of about 52 Mbps over twisted pair. Upstream data rates in asymmetric implementations tend to range up to about 3.3 Mbps. A typical VDSL distribution system includes a central office equipped with a host digital terminal (HDT) and arranged to operate as a hub between multiple video information providers (VIPs)/digital service providers (DSPs) and customer dwellings. In a fiber-to-the-neighborhood (FTTN) distribution system, optic fibers (e.g. OC-3c and OC-12c) are used to connect the HDT to a universal service access multiplexer (USAM), which is then connected to a network interface device (NID) located on the customer premises via twisted pair copper wire. A dedicated VDSL loop extends between the NID and an individual customer residence using either a dedicated twisted pair or telephone system twisted pair wire, and a customer interface device, such as a residential gateway or set top box, provides a connection point for a customer television or personal computer. A fiber-to-the-curb (FTTC) distribution system is similar except that a broadband network unit (BNU) is used in place of the USAM, and coaxial cable may be used to connect the BNU, NID, and set top box.
The VDSL signal format is used to carry signals to and from the customer. In these systems, the central office provisions each user for programming access rights, and maintains a profile database for each provisioned customer at the HDT to control the signals/channels that can be viewed by the customer.
In this environment, each of the various components and connections play a critical role in maintaining signal and network integrity. One element of particular concern involves the loop to each customer location. VDSL architectures operate at higher frequencies relative to the other xDSL technologies, and therefore require special considerations during testing to insure accurate collection of data. To date, a suitable test arrangement has yet to be developed which would allow accurate testing of a loop prior to actual provisioning of video/data service to the customer location. Because of service activation overhead and loop configuration database errors, a need exists for an economical and accurate testing process which can emphasize loop pre-qualification, noise measurement, and drop replacement.